High sedimentation rates in fjords provide excellent possibilities for
high resolution sedimentary and geochemical records over the Holocene.
As a baseline for an improved interpretation of geochemical data from
fjord sediment cores, this study aims to investigate the
inorganic/organic geochemistry of surface sediments and to identify
geochemical proxies for terrestrial input and river discharge in the
Trondheimsfjord, central Norway. Sixty evenly distributed surface
sediment samples were analysed for their elemental composition, total
organic carbon (Corg), nitrogen (Norg) and organic carbon stable isotopes (δ13Corg), bulk mineral composition and grain size distribution. Our results indicate carbonate marine productivity to be the main CaCO3
source. Also, a strong decreasing gradient of marine-derived organic
matter from the entrance towards the fjord inner part is consistent with
modern primary production data. We show that the origin of the organic
matter as well as the distribution of CaCO3 in
Trondheimsfjord sediments can be used as a proxy for the variable inflow
of Atlantic water and changes in river runoff. Furthermore, the
comparison of grain size independent Al-based trace element ratios with
geochemical analysis from terrigenous sediments and bedrocks provides
evidence that the distribution of K/Al, Ni/Al and K/Ni in the fjord
sediments reflect regional sources of K and Ni in the northern and
southern drainage basin of the Trondheimsfjord. Applying these findings
to temporally well-constrained sediment records will provide important
insights into both the palaeoenvironmental changes of the hinterland and
the palaeoceanographic modifications in the Norwegian Sea as response
to rapid climate changes and associated feedback mechanisms.